Wrap-Around Shielded Writer with Highly Homogeneous Shield Material

ABSTRACT

A perpendicular magnetic recording (PMR) head is fabricated with a main pole shielded laterally by a pair of side shields, shielded above by a trailing shield and shielded optionally below by a leading shield. The shields and the seed layers on which they are formed are formed of materials having substantially the same physical characteristics including the same material composition, the same hardness, the same response to processes such as ion beam etching (IBE), chemical mechanical polishing (CMP), mechanical lapping, such as the slider ABS lapping, the same coefficient of thermal expansion (CTE) as well as the same B s . Optionally, the trailing shield may be formed on a high B s  seed layer to provide the write head with improved down-track performance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the fabrication of a perpendicular magneticrecording (PMR) write head whose main pole is surrounded on all sides byshields formed of magnetic material. In particular it relates to theformation of such shields using layers of the same magnetic material sothat a consistent fabrication process can be employed and so that acorresponding consistent performance can be obtained.

2. Description of the Related Art

The increasing need for high recording area densities (up to 500 Gb/in²)is making the perpendicular magnetic recording head (PMR head) areplacement of choice for the longitudinal magnetic recording head (LMRhead).

By means of fringing magnetic fields that extend between two emergingpole pieces, longitudinal recording heads form small magnetic domainswithin the surface plane of the magnetic medium (hard disk). As recordedarea densities increase, these domains must correspondingly decrease insize, eventually permitting destabilizing thermal effects to becomestronger than the magnetic interactions that tend to stabilize thedomain formations. This occurrence is the so-called superparamagneticlimit. Recording media that accept perpendicular magnetic recording,allow domain structures to be formed within a magnetic layer,perpendicular to the disk surface, while a soft magnetic underlayer(SUL) formed beneath the magnetic layer acts as a stabilizing influenceon these perpendicular domain structures. Thus, a magnetic recordinghead that produces a field capable of forming domains perpendicular to adisk surface, when used in conjunction with such perpendicular recordingmedia, is able to produce a stable recording with a much higher areadensity than is possible using standard longitudinal recording.

Since their first use, the PMR head has evolved through severalgenerations. Initially, the PMR head was a monopole, but that design wasreplaced by a shielded head design with a trailing edge shield (TS),which provides a high field gradient in the down-track direction tofacilitate recording at high linear densities. Side shields (SS) thenbegan to be used in conjunction with the trailing edge shields, becauseit was necessary to eliminate the fringing side fields in order toincrease writing density still further. To further reduce the fringingin the down-track direction, thus reducing the length of the “writebubble” (the iso-field contour) down the track and improving writeperformance at a skew angle, a leading edge shield (LS) was alsoproposed, making the write head four-side shielded.

Despite the aforementioned advantages for the four-sided shieldeddesign, it does require additional design optimizations for all theshield layers. It is believed that a high saturation magnetic moment(B_(s)) seed layer, such as CoFe with a B, of 2.4 T (Tesla), for the TSwould improve the down-track field gradient. It is also traditionallybelieved that the LS and TS are somewhat “non-critical” layers and theyare often formed of very low moment material such as permalloy. As aresult, there will be a significant mismatch in material compositionsand moments for these layers, all of which are exposed at the ABS (airbearing surface) of the write head.

Several issues may arise as a result of materials and moment mismatches.First, the pole tip recession/protrusion may be very different betweenthe layers, as a result of hardness differences between the materialsand lapping rate variations during the slider lapping process thatdefines the final ABS. This may affect the magnetic spacing between thewrite pole and media during write operation, thereby adversely affectingperformance. For example, AFM (atomic force microscopy) images showhigher protrusion of the TS/SS seed layer relative to the surroundingmaterials. The seed layer has a B_(s)=2.2 T, whereas for the TS/SSshield materials themselves B_(s)=1.9 T. Another downside of higher seedlayer protrusion could be erasures from the shield corners due tocloseness of the seed layers to the media.

Another issue associated with the material/moment mismatches betweendifferent shield layers is the formation of domain walls at the layerinterfaces that may cause wide area track erasures (WATE). This could bea result of different material magnetostrictions causing differentdomain configurations in neighboring layers, which, in turn createdomain walls at the interfaces, or it could just be due to the momentmismatches producing magnetic charges at the interfaces which producestray fields.

Magnetic force microscopy applied to shield configurations with WS1(trailing shield) and PP3 (plated top layer) layers formed of materialshaving B_(s)=1.8 T and 1.0 T show evidence of domain walls propagatingfrom the MP region upward and stopping at the interface between thematerials. On the other hand, wrap-around shield configurations with allshields, SS, WS1 and PP3 made of the same B, material, show no suchdomain walls on the ABS and there is no WATE.

An additional disadvantage of using low B, materials in the LS and poleyoke layers is that in order to conduct the same amount of magnetic fluxas a material with twice the value of B_(s), would require twice thethickness. For example, the use of low B_(s) Ni₈₀Fe₂₀ vs. a NiFe, CoFeor CoNiFe alloy with a B_(s) of about 2.0 T. Larger metal volumesrequired of the lower B_(s) metals will cause larger protrusions duringtemperature increases either due to ambient increases or the heatgenerated by energizing currents.

Issues relevant to shield materials are described in the prior arts. Forexample, Terris et al. (U.S. Pat. No. 7,068,453) discloses side andtrailing shields formed of a soft magnetic material.

Gao et al. (U.S. Pat. No. 7,441,325) discloses a trailing shield formedof NiFe. Nix et al. (U.S. Pat. No. 7,367,112) teaches the formation of amain pole with trailing and side shields.

Guan et al. (U.S. Pat. No. 7,322,095, assigned to the present assignee)teaches a wrap-around shield, as do Jiang et al. (US Patent Application2009/0154026) and Hsiao et al. (US Patent Application 2009/0154019).

None of the prior art cited above address the problem addressed by thepresent invention nor do they disclose the structures and materials ofthe present invention.

SUMMARY OF THE INVENTION

A first object of this invention is to reduce the local protrusion of ashield layer due to mismatches in the materials used to form the layersand used to form various structures in the head itself.

A second object of the present invention is to eliminate the formationof domain walls at the interfaces between the TS, SS and LS portions ofa four sided magnetic shield due to mismatches in either the materialsor their moments, thereby eliminating wide area track erasures (WATE)that are associated with such domain walls.

A third object of the present invention is to reduce the pole tipprotrusion for a magnetic writer that uses a low B_(s) high thicknesscombination for certain shield layers, such as the LS and TS.

A fourth object of the present invention is to achieve the above statedobjects without diminishing the on-track and off-track performance ofthe head.

A fifth object of the present invention is to use the head so formed andprovided within a hard disk drive incorporating a slider mountedread/write head whose head is the head of the present invention, wherethe slider is mounted on a head gimble assembly within the hard diskdrive.

These objects will be achieved by means of a wrap-around shielded writehead whose main pole (MP) is surrounded by a TS (trailing shield), anoptional LS (leading shield) and two SS's (side shields). Note that insome figures, particularly in an ABS view, the trailing shield, TS isshown as two portions, which are labeled WS1 and PP3. The WS1 (writeshield 1) portion is the main part of the TS, whereas the portionlabeled PP3 is the ABS portion of the return yoke that completes themagnetic circuit with the main pole.

The non-magnetic write gap (WG) between the MP and the TS, thenon-magnetic side gap (SG) between the MP and the SS, and the leadinggap (LG) between the MP and the LS, are separately optimized andcontrolled. The WG is typically 15 to 50 nm, the SG is typically one toten times the width of the WG and the LG is typically one to twentytimes the WG. An important feature of the invention is that all shieldlayers, LS, TS and SS, including WS1 and PP3, an their respective seedlayer, have substantially the same material composition, the samehardness, the same response (eg. removal rate) to processes such as ionbeam etching (IBE), chemical mechanical polishing (CMP), mechanicallapping, such as the slider ABS lapping, and the same coefficient ofthermal expansion (CTE) as well as the same B_(s). By “substantially thesame,” is meant the fact that the physical characteristics (removalrate, CTE, B_(s)) among the various layers and their seeds may havesmall variations on, the order of 10%, of their respective nominalvalues. For example, a nominal B, of 2.0 T could have +/−0.1 T.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. la is a schematic representation of a first embodiment of thepresent invention showing a side cross-sectional view of aninductive-type write head in which is seen a main pole surrounded by theshields of the present invention at its trailing edge and leading edge,the side shields being there as well, but not visible in this view.

FIG. 1 b is a schematic ABS view of the write head of FIG. 1 a showingthe main pole tip surrounded by the shields of the present invention atits trailing edge, leading edge and sides.

FIG. 2 a is a schematic representation of a second embodiment of thepresent invention showing a side cross-sectional view of aninductive-type write head in which is seen a main pole surrounded by theshields of the present invention at its trailing edge and leading edge.This figure also shows a high B, seed layer that resides at the bottomof the trailing edge shield (WS1) just above the write gap (WG) layer.The side shields are also present, but not visible.

FIG. 2 b is a schematic ABS view of the write head of FIG. 2 a showingthe main pole tip surrounded by the shields of the present invention atits trailing edge, leading edge and sides as well as the high B, seedlayer..

FIG. 3 a is a schematic representation of a third embodiment of thepresent invention showing a side cross-sectional view of aninductive-type write head in which is seen a main pole surrounded by theshields of the present invention at its trailing edge but not at itsleading edge. Side shields are present, but not visible in this view.

FIG. 3 b is a schematic ABS view of the write head of FIG. 3 a showingthe main pole tip surrounded by the shields of the present invention atits trailing edge and sides.

FIG. 4 a is a schematic representation of a fourth embodiment of thepresent invention showing a side cross-sectional view of aninductive-type write head in which is seen a main pole surrounded by theshields of the present invention at its trailing edge and leading edge.As in the second embodiment, a high B_(s) seed layer is below thetrailing edge shield WS1.

FIG. 4 b is a schematic ABS view of the write head of FIG. 4 a showingthe main pole tip surrounded by the shields of the present invention atits trailing edge, leading edge and sides.

FIGS. 5 a-5 h are a series of schematic illustrations displaying theprocess flow that can be employed for fabricating any of the embodimentsillustrated above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiment of the present invention is a shielded polestructure for use within a perpendicular magnetic recording (PMR) head,in which the shields are all formed of materials having substantiallythe same physical characteristics including the same materialcomposition, the same hardness, the same response (eg. removal rate) toprocesses such as ion beam etching (IBE), chemical mechanical polishing(CMP), mechanical lapping, such as the slider ABS lapping, and the samecoefficient of thermal expansion (CTE) as well as the same B_(s). By“substantially the same,” is meant the fact that the physicalcharacteristics (removal rate, CTE, B_(s)) among the various layers andtheir seeds may have small variations on, the order of 10%, of theirrespective nominal values. For example, a nominal B, of 2.0 T could have+1-0.1 T.

Referring first to FIG. 1 a, there is shown a schematic sidecross-sectional view of a typical inductive type PMR write head that isshielded in the manner provided by the present invention. This viewshows rectangular cross-sections of the inductive coil windings as wellas an upper yoke (16). The MP (10) is preferably formed of materialhaving a high B_(s) ranging from 2.2 T to 2.4 T and can be formed ofmagnetic materials such as NiFe, CoFe, CoNiFe, CoFePd, or CoFeN. Thematerials for the leading (LS) and trailing (WS1; PP3) shields (LS(20)), (WS1 (30); PP3(16)), including their seed layers, can also bemade of any of these alloys and it is preferred that the material have aB_(s) ranging from 1.5 T to 2.2 T. By using materials in these ranges,as compared to prior art materials in the range of approximately 1.0 T,the thicknesses of the TS and SS can be reduced by half, which willresult in reduced pole tip protrusion (PTP) and improved head-mediaspacing margin.

Referring next to FIG. 1 b, there is shown the fabrication of FIG. 1 afrom the ABS perspective. There can now be clearly seen thesymmetrically disposed side shields (SS) (40) and the side gap layers(45) separating the outside edge of the main pole (10) from the inneredge of the side shields. There is also clearly seen the write gap layer(25) separating the upper surface of the main pole (10) from the loweredge of the trailing shield, WS1 (30). Correspondingly, a lower gaplayer (15) separates the upper edge of the leading shield (20) from thelower edge of the main pole (10). In this embodiment, each shield layerhas a seed layer (not shown) that is formed of the same material as theshield layer itself.

Referring now to FIG. 2 a, there is shown a schematic side view of thesame inductive type PMR write head of FIG. 1 a that is now shielded inthe manner provided by a second embodiment of the present invention.This embodiment differs from that described in FIG. 1 a by the presenceof a high B_(s) (>2.0T) seed layer (35) that is patterned to be justwide enough (in its lateral extent) to cover the write gap layer (25) asit extends laterally between the inner edge surfaces of the two sideshields (see FIG. 2 b).

Referring to schematic FIG. 2 b, there is shown the high B_(s) seedlayer that is wide enough to cover the entire width (lateral extent) ofthe write gap layer (25). The write gap layer extends over the trailingedge of the main pole and the trailing edge surfaces of the two sidegaps (45). This higher B_(s) seed layer is first deposited along theentire write gap layer surface and the upper surfaces of the two sideshields (40), which have all been properly planarized by a CMP process.The higher B_(s) seed layer is then patterned by an IBE to form anextremely narrow layer as shown in the figure, extending only a short,lateral distance of approximately +/−0.3 microns to either side of themain pole. The use of a high B_(s) seed layer in this position providesa high B_(s) within a region of the trailing edge shield, WS1, layerprecisely where it is required to improve the on-track field gradientalong the trailing edge side of the track. The advantages of theidentical shield layer and seed layer materials at all other locationsexcept for this small portion (35) still hold true, but the additionaladvantages of the improved on-track field gradient can also be obtained.It should be noted that, while strictly speaking, the presence of thesmall high B_(s) region of the trailing edge shield might be said tocontradict the designation of the entire shield as being of the samematerial, the volume of shield material with high B_(s) is so smallcompared to the volume of the entire shield, that all of the advantagesand objects of the invention that result from the same shield materialsbeing used are still met.

As in the embodiment of FIGS. 1 a and 1 b, the MP (10) is preferablyformed of material having a high B_(s) ranging from 2.2 T to 2.4 T andcan be formed of magnetic materials such as NiFe, CoFe, CoNiFe, CoFePd,or CoFeN. The leading and trailing shields (LS (20)), (WS1 (30))materials, including their seed layers, can also be made of any of thesealloys and it is preferred that the material have a B, ranging from 1.5T to 2.2 T. By using materials in these ranges, as compared to prior artmaterials in the range of approximately 1.0 T, the thicknesses of the TSand SS can be reduced by half, which will result in reduced pole tipprotrusion (PTP) and improved head-media spacing margin.

Referring next to FIG. 3 a, there is shown the PMR write head of FIGS. 1a and 2 a, except that there is no leading shield in this embodiment.

Referring now to FIG. 3 b, there is shown the fabrication of FIG. 3 afrom the ABS perspective where the leading edge shield is no longerformed. There can now be clearly seen the trailing edge shield (30), thewrite gap layer (35) that separates the main pole (10) from the trailingedge shield, WS1, (30), the side shields (SS) (40) and the two side gaps(45) separating the outside edge of the main pole (10) from the inneredge of the side shields.

Referring next to FIG. 4 a, there is shown schematically the fabricationof FIG. 2 a, except that there is no longer formed a leading shield.

Referring next to FIG. 4 b, there is shown schematically the fabricationof FIG. 4 a, from an ABS perspective, where the leading edge shield isno longer formed. The “Hi-B, seed” layer, which is the seed layer of ofhigh B_(s) material (35) is still present, as are all other elements ofFIG. 2 b.

Referring now to schematic FIG. 5 a, there is shown the first of aseries of process steps through which the embodiments of the presentinvention can be fabricated. First, there is shown a substrate (100),which can be a layer of non-magnetic metal such as Ru or Ta, on whichhas been formed a dielectric layer (200) of Al₂O₃ to a thickness ofbetween approximately 0.2 and 0.6 microns. The dielectric layer will beused as a form in which to plate the main pole of the write head.

Referring to schematic FIG. 5 b, there is shown the formation of acavity in layer (200). The cavity is etched by a photolithographic andetching process, which can be an IBE. The shape of the cavity iscongruent with the desired shape of the main pole to be plated withinit. As we shall see, below, in FIG. 5 f, the cavity can terminate at thesubstrate, which will enable the formation of a shielded pole that lacksthe leading edge shield, or in this case, it can terminate within thebody of the dielectric layer, to leave space for the formation of aleading edge shield.

The cavity is then lined on bottom and sides with a layer (400) ofnon-magnetic metal such as Ru or Ta. A main pole (10) is then platedwithin the lined cavity and the upper surface of the fabrication isplanarized by a CMP process or the like. The main pole is preferablyformed of material having a high B_(s), ranging from 2.2 T to 2.4 T andit can be formed of magnetic materials such as NiFe, CoFe, CoNiFe,CoFePd, or CoFeN.

Referring next to schematic FIG. 5 c, there is shown the fabrication ofFIG. 5 b, wherein the dielectric material layer ((200) in FIG. 5 b),laterally disposed from the main pole (10) and beneath the main pole isremoved by a wet etch, leaving behind the uncovered metallic substrate(100). The partially lined pole tip (lined on its sides and bottom), asshown, floats over the substrate, although it is supported behind theplane of the figure. Although it is not shown in the figure, the uppersurface of the already plated pole can be protected by a mask duringthis wet etch process so that it is not damaged.

Referring next to schematic FIG. 5 d, there is shown the fabrication ofFIG. 5 c in which any protective mask layer has been removed and anatomic layer deposition (ALD) process has been used to deposit acontinuous gap layer (500), that is contiguous with the partially linedmain pole. This layer, which can be a layer of Ru or Al₂O₃ willultimately form (with its upper portion) a write gap layer ((25) in FIG.5 e) between the trailing shield and the main pole (10), side gap layers(45) in FIG. 5 e) between the side shields and the main pole and aleading gap layer ((15) in FIG. 5 e), between the leading shield and themain pole, if a leading shield is formed.

Referring now to FIG. 5 e, there is shown schematically the result of asingle plating step on the substrate (100) that forms the completelysurrounding and continuous shield configuration. This shieldconfiguration includes two side shield portions (40), a trailing shieldportion (30) and a leading shield portion (20). The shield is separatedfrom the main pole (10) by side gap layers (45), a write gap layer (25)and a leading gap layer (15), when the leading shield is present, as itis here.

As already noted, the MP (10) has been preferably formed of materialhaving a high B_(s), ranging from 2.2 T to 2.4 T and is formed ofmagnetic materials such as NiFe, CoFe, CoNiFe, CoFePd, or CoFeN. Thematerials forming the leading and trailing shields, including their seedlayers, can also be made of any of these alloys and it is preferred thatthe material have a B, ranging from 1.5 T to. 2.2 T. The shieldconfiguration is substantially of uniform thickness (in the dimensionnormal to the ABS) because of the use of the same material in all of itsportions.

In an embodiment in which a leading edge shield is not to be formed, thefabrication can proceed by substituting FIG. 5 f for FIG. 5 a, formingthe lined cavity for the MP plating in the layer (200) of so that itdirectly contacts the substrate material (100) (eg. the Ru or Tametallic substrate).

In an alternative embodiment, where it is desired to utilize a high B,seed layer as shown in FIGS. 2 a and 2 b and described above, it can bedeposited on the top surface of the write gap layer at a point in thefabrication process before the completed plating as shown in FIG. 5 e.This can be done as follows. Referring to FIG. 5 g, there is shown thefabrication of FIG. 5 e where the plating of the leading and sideshields has been terminated where the side shields (40) have reachedtheir correct height. At that point, the upper surface of thefabrication is planarized. Then a high B_(s) seed layer is depositedover the upper surface and is patterned using an IBE (ion beam etch) toremove outer (shaded) portions (350) and to leave only a narrow centralportion (35) extending laterally to each side of the main pole by, forexample, +1-0.3 microns.

After the formation of the patterned seed layer (35) in FIG. 5 g, theplating process is continued, as in FIG. 5 h, to form the trailing edgeshield (30) above and continuous with the side shields (40) and tothereby complete the surrounding shield configuration. It is understoodthat in this embodiment, also, the leading edge shield is optional.

As is understood by a person skilled in the art, the preferredembodiment of the present invention is illustrative of the presentinvention rather than limiting of the present invention. Revisions andmodifications may be made to methods, materials, structures anddimensions employed in forming and providing a PMR head having a mainpole-tip surrounded by a magnetic shield configuration formed of thesame magnetic materials, while still forming and providing such a PMRhead and pole and its method of formation in accord with the spirit andscope of the present invention as defined by the appended claims.

What is claimed is:
 1. A PMR write head comprising: a main pole; amagnetic shield at least partially surrounding said main pole and formedin the ABS plane of said pole tip, wherein said shield includes atrailing shield portion and a portion including two side shields,wherein said trailing and side shield portions are formed of the samemagnetic material and are formed using the same seed layers and form asubstantially continuous structure, and wherein said trailing and sideshield portions are separated from said main pole by a substantiallycontinuous non-magnetic layer, wherein said non-magnetic layer forms awrite gap layer extending laterally between inner edges of said sideshields and along a trailing edge of said main pole and wherein saidnon-magnetic layer forms a side gap between side edges of said main poleand inner edges of said side shields.
 2. The PMR write head of claim 1further including a leading edge shield portion formed beneath a leadingedge of said main pole and continuous with said trailing edge shieldportion and said side shield portions and thereby completely surroundingsaid main pole and wherein said leading edge shield portion is separatedfrom said main pole by a leading edge gap that is formed as a portion ofsaid non-magnetic layer.
 3. The PMR write head of claim 1 wherein saidmain pole is formed of material having a high B_(s), ranging from 2.2 Tto 2.4 T.
 4. The PMR write head of claim 3 wherein said main pole isformed of NiFe, CoFe, CoNiFe, CoFePd, or CoFeN.
 5. The PMR write head ofclaim 1 wherein said leading and trailing shields and their seed layers,are formed of material having a B_(s) ranging from 1.5 T to 2.2 T. 6.The PMR write head of claim 5 wherein said material is NiFe, CoFe,CoNiFe, CoFePd, or CoFeN.